Silicon-containing compound, urethane resin, stretchable film, and method for forming the same

ABSTRACT

The present invention provides a silicon-containing compound shown by the following formula (1): 
                         
wherein R 1 , R 2 , R 3 , R 4 , R 5 , and R 6  each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by —(OSiR 7 R 8 ) n —OSiR 9 R 10 R 11 ; R 7 , R 8 , R 9 , R 10 , and R 11  have the same meanings as R 1  to R 6 ; “n” is an integer in the range of 0 to 100; and “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms. This provides a stretchable film that has excellent stretchability and strength, with the film surface having excellent repellency, and a method for forming the same; as well as a urethane resin used for the stretchable film; and a silicon-containing compound to be a material of the urethane resin.

TECHNICAL FIELD

The present invention relates to a stretchable film that combine stretchability, strength, and repellency, and a method for forming the same; as well as a urethane resin used for the stretchable film; and a silicon-containing compound to be a material of the urethane resin.

BACKGROUND ART

In recent years, wearable devices have been developed progressively with the spread of Internet of Things (IoT). Representative examples thereof include a watch and glasses that can be connected with internet. Wearable devices that can always monitor physical conditions are also necessary in a medical field and a sports field, and are expected to be a growth field in the future.

Wearable devices include a form that is adhered to a body or adhered to a stretchable cloth that is closely adhered to a body to monitor physical conditions constantly. Such a wearable device is generally composed of a bio-electrode to detect electric signals from a body, wiring to send the electric signals to a sensor, a semiconductor chip to be the sensor, and a battery. Normally, an adhesive pad is necessary to be adhered to skin. The structures of a bio-electrode, wiring around the same, and an adhesive pad are specifically described in Patent Literature 1. In the wearable device described in Patent Literature 1, a silicone based adhesive film is disposed around the bio-electrode, and the bio-electrode is connected with a sensor device by stretchable silver wiring in the shape of bellows coated with a stretchable urethane film.

Urethane films have high stretchability and strength to possess excellent mechanical properties as coating films for stretchable wiring. The urethane film, however, has hydrolytic properties to cause degradation, thereby inducing a disadvantage of lowering the stretchability and the strength due to hydrolysis. On the other hand, silicone films are free from hydrolytic properties, but has a disadvantage of lower strength.

Accordingly, it has been conducted to investigate silicone-urethane polymers with each polymer main chain having both of a urethane bond and a siloxane bond. The cured product of this polymer has higher strength than single silicone, and lower hydrolytic properties than single polyurethane. The cured product of this polymer, however, fails to equal the strength of single polyurethane and the repellency of single silicone, only giving strength and repellency in the middle of those of silicone and polyurethane.

On the other hand, a material in which polyurethane and silicone are blended has been investigated. For example, Patent Literature 2 and Patent Literature 3 describe a material in which non-reactive silicone and crosslinkable polyurethane are blended. In a film formed from such a material, silicone comes up to the surface of a cured polyurethane film (bleed out) to improve the repellency of the film surface. In such a film, however, the silicone is not crosslinked, which causes peeling of silicone on the film surface to be tend to lower the repellency. Additionally, without a surface, the silicone does not come up to the surface of the film. Accordingly, a compression molded material in which the film is sandwiched between sheets does not show high repellency.

Additionally, a diol material has been proposed for synthesizing polyurethane having a siloxane side chain. Patent Literatures 4 and 5 each describe a diol compound for forming polyurethane in which silicone is attached to the side chain. The side chain silicone group shown therein is a linear silicone in which the siloxane terminal is bonded to the diol compound.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Laid-Open Publication No. 2004-033468

Patent Literature 2: Japanese Patent Laid-Open Publication No. 2011-194757

Patent Literature 3: Japanese Patent Laid-Open Publication No. 2013-139534

Patent Literature 4: Japanese Patent No. 2583412

Patent Literature 5: Japanese Patent No. 2624060

SUMMARY OF THE INVENTION Technical Problem

In view of these backgrounds, it has been demanded for developing a stretchable film that has excellent stretchability and strength equal to those of polyurethane, together with excellent repellency equal to that of silicone, and a method for forming the same.

The present invention has been accomplished to solve the foregoing problems, and an object thereof is to provide a stretchable film that has excellent stretchability and strength, with the film surface having excellent repellency, and a method for forming the same; as well as a urethane resin used for the stretchable film; and a silicon-containing compound to be a material of the urethane resin.

Solution to Problem

To solve the problems, the present invention provides a silicon-containing compound shown by the following formula (1):

wherein R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by —(OSiR⁷R⁸)_(n)—OSiR⁹R¹⁰R¹¹; R⁷, R⁸, R⁹, R¹⁰, and R¹¹ have the same meanings as R¹ to R⁶; “n” is an integer in the range of 0 to 100; and “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms.

The inventive silicon-containing compound can be a material of a urethane resin used for a stretchable film, making it possible to form a stretchable film that has excellent stretchability and strength, with the film surface having excellent repellency.

The silicon-containing compound of the formula (1) is preferably shown by the following formula (2).

Having a structure like this, the silicon-containing compound of the formula (1) can be a material of a urethane resin used for a stretchable film, making it possible to form a stretchable film with more improved repellency.

The present invention also provides a urethane resin comprising a structure shown by the following formula (3):

wherein R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by —(OSiR⁷R⁸)_(n)—OSiR⁹R¹⁰R¹¹; R⁷, R⁸, R⁹, R¹⁰, and R¹¹ have the same meanings as R¹ to R⁶; “n” is an integer in the range of 0 to 100; and “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms.

The inventive urethane resin is capable of forming a stretchable film that has excellent stretchability and strength, with the film surface having excellent repellency.

The urethane resin preferably has a structure containing a (meth)acrylate group at a terminal thereof shown by the following formula (4):

wherein R¹, R², R³, R⁴, R⁵, R⁶, and “A” have the same meanings as defined above; R¹² represents a hydrogen atom or a methyl group; “p” and “q” each represent a number of unit in one molecule, and are integers in the range of 1≤p≤100 and 1≤q≤3.

The urethane resin like this is capable of forming a stretchable film that has excellent stretchability and strength equal to or superior to those of polyurethane, with the film surface having excellent repellency and smooth touch with less stickiness.

The present invention also provides a stretchable film comprising the urethane resin described above.

The inventive urethane resin-containing stretchable film provides excellent stretchability and strength, with the film surface having excellent repellency.

It is preferable that the stretchable film exhibit a stretching property of 40 to 500% in a tensile test regulated by JIS K 6251.

Having such a stretching property, the stretchable film is usable for a coating film of a stretchable wiring particularly favorably.

It is preferable that the stretchable film is used as a film to be in contact with a conductive wiring having stretchability.

The inventive stretchable film is applicable to these uses particularly favorably.

The present invention also provides a method for forming a stretchable film, comprising:

mixing a compound shown by the following formula (1) and a compound having an isocyanate group to make a mixture,

wherein R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by —(OSiR⁷R⁸)_(n)—OSiR⁹R¹⁰R¹¹; R⁷, R⁸, R⁹, R¹⁰, and R¹¹ have the same meanings as R¹ to R⁶; “n” is an integer in the range of 0 to 100; and “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms;

forming a film of the mixture; and

curing the film by heating.

The inventive method for forming a stretchable film makes it possible to easily produce a stretchable film that has excellent stretchability and strength, with the film surface having excellent repellency.

In this method, the compound shown by the formula (1) is preferably a compound shown by the following formula (2).

Using the silicon-containing compound of the formula (1) with such a structure, it is possible to easily produce a stretchable film with more improved repellency.

The present invention further provides a method for forming a stretchable film, comprising:

forming a film of a compound having a (meth)acrylate group at a terminal thereof shown by the following formula (4):

wherein R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by —(OSiR⁷R⁸)_(n)—OSiR⁹R¹⁰R¹¹; R⁷, R⁸, R⁹, R¹⁰, and R¹¹ have the same meanings as R¹ to R⁶; “n” is an integer in the range of 0 to 100; “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms; R¹² represents a hydrogen atom or a methyl group; “p” and “q” each represent a number of unit in one molecule, and are integers in the range of 1≤p≤100 and 1≤q≤3; and

curing the film by heating and/or light irradiation.

In the inventive method for forming a stretchable film, it is possible to combine heat curing and photo-curing as described above.

Advantageous Effects of Invention

As described above, the inventive stretchable film exhibits excellent stretchability and strength equal to or more than those of polyurethane, together with high repellency such that the film surface has excellent repellency that is equal to or superior to that of silicone having a main chain composed of siloxane bond. The inventive urethane resin is usable for such stretchable films favorably. Additionally, the inventive silicon-containing compound is usable for materials of such urethane resins. The inventive stretchable film is based on a urethane resin in which two silicon-containing groups are attached to the side chains. Accordingly, the repellency of the stretchable film is efficiently improved by the two silicon-containing groups attached to the side chains in small quantity. When two silicon-containing groups are attached to side chains, the electron pair of a urethane bond is pushed to the opposite side of the silicon-containing side chains, which increases the hydrogen bonding property to increase the strength. In general, introduction of a silicon-containing group lowers the strength though it improves the repellency. In case of structures of the present invention, however, both of the strength and the repellency are successfully improved, and a innovated material is provided. The two silicon-containing groups on the side chains usually face the surface side of the stretchable film, thereby making the repellency higher even when the stretchable film is formed in a sealed state in which the both sides of a composition for forming the stretchable film has been sandwiched between sheets, for example. When the stretchable film like this is brought into contact with a conductive wiring or used for coating a side or the both sides of a conductive wiring, the obtained stretchable wiring film has a surface with excellent repellency not only has excellent stretchability and strength. Accordingly, the inventive stretchable film is usable for a wearable device particularly suitably as a stretchable film that is capable of loading all of the bio-electrode(s) and the sensor(s) not only a wiring unit to connect the bio-electrode and the sensor. The inventive method for forming a stretchable film makes it possible to easily form a highly repellent stretchable film that has excellent stretchability and strength equal to those of polyurethane, with the film surface having excellent repellency that is equal to or superior to that of silicone having a main chain composed of siloxane bond.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view showing an electrocardiograph in a state being coated with the inventive stretchable film;

FIG. 2 is a schematic drawing of the electrocardiograph in FIG. 1 viewed from the bio-electrode;

FIG. 3 is a sectional view showing a conventional electrocardiograph;

FIG. 4 is a schematic drawing of the electrocardiograph in FIG. 3 viewed from the bio-electrode;

FIG. 5 is a sectional view showing an electrocardiograph in a state being in contact with a substrate and coated with the inventive stretchable film;

FIG. 6 is a sectional view showing the inventive stretchable film on which a bio-electrode, a self-adhesive part, and wiring are formed, and a center device is connected;

FIG. 7 is a sectional view showing the wiring and the center device in FIG. 6 in a state being coated with the inventive stretchable film;

FIG. 8 is a sectional view showing the inventive stretchable film, formed on a fabric, on which wiring and an electrode are formed, and a center device is connected;

FIG. 9 is a sectional view showing the wiring and the center device in FIG. 8 in a state being coated with the inventive stretchable film.

DESCRIPTION OF EMBODIMENTS

As described above, polyurethane has a sufficient stretchability and strength, but also has a drawback of low repellency to lower the strength and stretchability due to hydrolysis; silicone has a drawback of lower strength although the repellency is high. The cured material of a silicone urethane polymer, which contains both of urethane bonds and siloxane bonds in the main chain, has a problem that the strength and repellency are in the middle of those of polyurethane and silicone, and inferior to the strength of polyurethane alone or the repellency of silicone alone. Additionally, in the method for forming a film with improved repellency by blending polyurethane and silicone followed by baking to unevenly distribute the silicone to the film surface, the film surface has lower strength, and the silicone does not come up to the surface of the film unless there is a surface, causing a drawback of unimproved repellency in a sealed state in which the film has been sandwiched between sheets, for example. Additionally, this method requires to blend a solvent with a boiling point in a range of 100 to 200° C. in order to accelerate the uneven distribution of the silicone to the surface, and fails to form a film without a solvent, causing a drawback such that the composition or film-forming process is limited. On the basis of these backgrounds, it has been required to develop a stretchable film that has excellent stretchability and strength equal to those of polyurethane, with the film surface having sufficiently high strength and surface hardness as well as excellent repellency that is equal to or superior to that of silicone, together with a method for forming the same.

Accordingly, the present inventors have diligently investigated to achieve the above objects. As a result, the inventors have found that the film based on a resin having a urethane bond in the main chain as well as ether groups having high flexibility and two of highly repellent silicon-containing groups on the side chains is excellent in stretchability and strength while having high repellency, and forms a stretchable film that has excellent stretchability and strength equal to or superior to those of polyurethane with the film surface having excellent repellency that are equal to or superior to those of silicone, and is particularly favorable as a coating film of a stretchable wiring, a device, and a sensor in a wearable device; thereby bringing the present invention to completion.

That is, the present inventors have found that the film composed of a resin having a urethane bond in the main chain, together with an ether group and a silicon atom in each of the two side chains, has stretchability and strength equal to those of polyurethane, has high repellency, and is useful as a stretchable film for coating a bio-electrode.

That is, the present invention is a silicon-containing compound shown by the following formula (1):

wherein R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by —(OSiR⁷R⁸)_(n)—OSiR⁹R¹⁰R¹¹; R⁷, R⁸, R⁹, R¹⁰, and R¹¹ have the same meanings as R¹ to R⁶; “n” is an integer in the range of 0 to 100; and “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms.

The present invention also provides a urethane resin comprising a structure shown by the following formula (3):

wherein R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by —(OSiR⁷R⁸)_(n)—OSiR⁹R¹⁰R¹¹; R⁷, R⁸, R⁹, R¹⁰, and R¹¹ have the same meanings as R¹ to R⁶; “n” is an integer in the range of 0 to 100; and “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms.

The present invention also provides a method for forming a stretchable film, comprising:

mixing a compound shown by the following formula (1) and a compound having an isocyanate group to make a mixture,

wherein R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by —(OSiR⁷R⁸)_(n)—OSiR⁹R¹⁰R¹¹; R⁷, R⁸, R⁹, R¹⁰, and R¹¹ have the same meanings as R¹ to R⁶; “n” is an integer in the range of 0 to 100; and “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms;

forming a film of the mixture; and

curing the film by heating.

Hereinafter, the present invention will be described specifically, but the present invention is not limited thereto.

<Silicon-Containing Compound>

The inventive silicon-containing compound is shown by the following formula (1).

In the formula, R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by —(OSiR⁷R⁸)_(n)—OSiR⁹R¹⁰R¹¹; R⁷, R⁸, R⁹, R¹⁰, and R¹¹ have the same meanings as R¹ to R⁶; and “n” is an integer in the range of 0 to 100.

Illustrative examples of the alkyl group of R¹ to R¹¹ include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an isopropyl group, an isobutyl group, a tert-butyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group.

In the formula, “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms.

Illustrative examples of “A” include a methylene group, an ethylene group, a propylene group, and a butylene group.

In the silicon-containing compound shown by the formula (1), each of the dialcohol moieties is primary, thereby having higher reactivity to isocyanate, making it possible to form a urethane bond easily. Another merit of using a silicon-containing compound that contains primary dialcohol is that the urethane bond formed by reaction with isocyanate has higher degree of freedom of rotation, which increases the hydrogen bonding tendency between the urethane bonds, thereby making it possible to form a film with improved strength.

Additionally, the inventive silicon-containing compound shown by the formula (1) is a diol compound having ether groups and silicon-containing groups in two side chains thereof. The production method of the inventive silicon-containing compound is not particularly limited, but it can be obtained by the reaction of propanediol having two double bond-containing ether groups in the side chains and a silicon compound having SiH groups in the siloxane chain in the presence of a platinum catalyst, for example. The hydroxyl groups may be remained unprotected, but can be protected by trimethylsilyl groups or acid-libable groups previously, followed by deprotecting thereof after the reaction since hydroxyl groups sometimes lower the activity of platinum catalysts.

The synthesis method of propanediol having two double bond-containing ether groups in the side chains, which can be a raw material of the inventive silicon-containing compound, is not particularly limited and includes a method in which two of the four hydroxy groups of pentaerythritol are previously protected, and the remaining two hydroxy groups are converted to alkenyl ethers to form a precursor, followed by reaction of the precursor and a silicon compound having SiH groups in the siloxane chain in the presence of a platinum catalyst, and deprotection of the protective groups of the two hydroxy groups.

Illustrative examples of the inventive silicon-containing compound specifically include the following, but are not limited thereto.

In the formulae, each repeating number represents the average value.

In the formulae, each repeating number represents the average value.

In general, silicone with shorter chain length forms a stretchable film in which the strength is less lowered. On the other hand, silicone with longer chain length brings more improved repellency. Silicone with a branched structure makes it possible to improve the repellency with shorter chain length. Accordingly, it is more preferable that the inventive silicon-containing compound be shown by the following formula (2).

The inventive silicon-containing compound like this can be a material of a urethane resin used for a stretchable film, making it possible to form a stretchable film that has excellent stretchability and strength equal to those of polyurethane, with the film surface having excellent repellency equal to or superior to that of silicone in which the main chain is composed of a siloxane bond.

<Urethane Resin (Urethane Polymer)>

The inventive urethane resin has a structure shown by the following formula (3).

In the formula, R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by —(OSiR⁷R⁸)_(n)—OSiR⁹R¹⁰R¹¹; R⁷, R⁸, R⁹, R¹⁰, and R¹¹ have the same meanings as R¹ to R⁶; and “n” is an integer in the range of 0 to 100.

In the formula, “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms.

Concrete examples of the inventive urethane resin is not particularly limited. As the side chain having a silicon-containing group, it is possible to apply the same ones illustrated in the concrete examples of the silicon-containing compound described above.

The urethane resin preferably comprises a hard segment composed of the moiety sandwiched between the two urethane bonds shown by the formula (3) and a soft segment composed of a moiety of polyether, polyester, and/or polycarbonate for extending the chain length.

The structure shown by the formula (3) attains improved strength by hydrogen bond. It is conceived that such a structure as shown by the formula (3) forms a crystallized structure. This will be described specifically in the following.

The inventive urethane resin has a structure characterized by a plurality of pendant groups each having an ether group and a silicon atom in the side chain as shown in the formula (3). The existing highly repellent silicon-containing groups push the highly hydrophilic urethane bonds to the opposite side to orient the localized electrons of the urethane bonds outward, thereby forming more strong hydrogen bonds. In case of introducing silicone into the main chain, the strength is lowered although the repellency is improved. In case of introducing silicon-containing groups into the side chain as in the present invention, however, not only the repellency but also the strength is improved by the reason described above. It is also possible to dramatically improve the repellency and the strength by introducing a plurality of silicon-containing groups in the side chains.

In general, a highly stretchable film is flexible, and such a flexible film with high stretchability cause to increase the self-adhesiveness as the film becomes thinner, thereby making the films tend to adhere with each other to be difficult to release. In case of stretchable films to be adhered to skins, a thinner stretchable film is required to decrease the deficiency in wear comfort when it is adhered. Introduction of silicon-containing groups allows the film surface to decrease the self-adhesiveness or tacky feel to be non-greasy. In such thin films that the self-adhesiveness increases, the film surface is allowed to decrease the greasy feeling by introducing a plurality of silicon-containing groups into side chains of the compound to be a material of the thin film. Since the film loses the strength as it becomes thinner, the silicon-containing groups are introduced into the side chain not into the main chain in the inventive urethane resin as described above to improve the strength.

The inventive urethane resin more preferably has a structure that contains a (meth)acrylate group at the terminal shown by the following formula (4).

In the formula, R¹, R², R³, R⁴, R⁵, R⁶, and “A” have the same meanings as defined above; R¹² represents a hydrogen atom or a methyl group; “p” and “q” each represent a number of unit in one molecule, and are integers in the range of 1≤p≤100 and 1≤q≤3. [Production Method of Urethane Resin]

The production method of the inventive urethane resin is not particularly limited, but it is preferably produced such that the inventive silicon-containing compound described above is used as a raw material, and this silicon-containing compound is allowed to react with a compound that contains isocyanate groups (an isocyanate compound).

The isocyanate compound used for the reaction with the inventive silicon-containing compound is not particularly limited, and the illustrative examples thereof include the following.

In the formulae, “s” is an integer of 1 or more.

Among the isocyanate compounds described above, the compound having a (meth)acrylate group particularly makes it possible to give the resin having the structure containing a (meth)acrylate group at the terminal shown by the formula (4) through the reaction with the inventive silicon-containing compound. It is also possible to obtain a polymer that has a structure containing a (meth)acrylate group at the terminal shown by the formula (4) by the reaction of the inventive silicon-containing compound and reaction product of a compound having a hydroxy group-containing (meth)acrylate group and an isocyanate compound.

As the isocyanate compound described above, it is preferable to use a compound having blocked isocyanate groups in which the isocyanate groups have been protected by substituents. This facilitates the control of the reaction even when the reactivity of the isocyanate compound and the silicon-containing compound shown by the formula (1) is high. The isocyanate compound can react with moisture in the air to inactivate the isocyanate groups during the storage, and have to be carefully stored such as sufficient moistureproofing. These phenomena can be prevented by the compound having blocked isocyanate groups.

The blocked isocyanate group is a blocked group that is deprotected by heating to be an isocyanate group. Illustrative examples thereof include isocyanate groups substituted with alcohol, phenol, thioalcohol, imine, ketimine, amine, lactam, pyrazole, oxime, and β-diketone.

In the use of a compound that has blocked isocyanate groups, a catalyst may be added to decrease the temperature for deprotecting the blocked isocyanate groups. This catalyst is not particularly limited, and known examples thereof include organic tin compounds such as dibutyl tin dilaurate, bismuth salts, and zinc carboxylate such as zinc 2-ethylhexanoate and zinc acetate.

As the dissociation catalyst for a blocked isocyanate, it is preferable to use zinc α,β-unsaturated carboxylate as described in JP 2012-152725A.

When the inventive urethane resin is prepared, a compound having a plurality of hydroxy groups can be added in addition to the silicon-containing compound shown by the formula (1) and the isocyanate compound. Addition of the compound having a plurality of hydroxy groups like this makes it possible to extend the chain length or crosslink the molecules of the inventive urethane resin.

The compound having a plurality of hydroxy groups is not particularly limited, and the illustrative examples thereof include the following.

Additionally, a compound having an amino group can also be added. When an isocyanate group reacts with an amino group, a urea bond is formed. The moieties of a urethane bond and a urea bond is a hard segment, and improves the strength through their hydrogen bonds. The strength is successfully improved by the addition of urea bonds not only by urethane bonds.

Among the soft segments formed from a diol compound for extending the chain length containing polyether, polyester, or polycarbonate, most stretchable one is polyether, followed by polyester and polycarbonate, in which order the stretchability decreases. On the other hand, the order of tensile strength is in the opposite order to the order of stretchability. The strength and the stretchability can be controlled by selecting the kind of the soft segment or repeating unit.

The inventive urethane resin preferably has a weight average molecular weight of 500 or more. They can be favorably used for the inventive stretchable film. The upper limit of the weight average molecular weight of the resin is preferably 500,000 or less.

The inventive urethane resin having a structure with urethane bonds shown by the formula (3) can be used for forming fibers, not only for the use of forming a stretchable film that will be described later. The fiber material can be woven to form a stretchable fabric or formed to an unwoven fabric. The inventive urethane resin can also be used for coating polyester or cotton to give a fabric or non-woven fabric.

The urethane resin having urethane bonds shown by the formula (3) can be formed into a urethane gel. A highly repellent and highly elastic gel with low hardness can be formed by reducing the crosslinking density. The soft gel has comfortable touch and has repellent properties to repel perspiration or water.

<Stretchable Film>

The inventive stretchable film is a cured material of a composition containing the inventive urethane resin. As the urethane resin to be contained, the ones described above can be used.

The inventive stretchable film is preferably the one that exhibits a stretching property of 40 to 500% in a tensile test regulated by JIS K 6251. With such a stretching property, the inventive stretchable film can be used particularly favorably for a coating film of stretchable wiring.

The inventive stretchable film is preferably used for a film to be in contact with a conductive wiring having stretchability. The inventive stretchable film can be favorably used for these uses.

The inventive stretchable film described above has excellent stretchability and strength equal to those of polyurethane, with the film surface having excellent repellency that is equal to or superior to that of silicone.

<Method for Forming Stretchable Film>

The present invention provides a method for forming a stretchable film, comprising:

mixing a compound shown by the following formula (1) and a compound having an isocyanate group to make a mixture,

forming a film of the mixture; and

curing the film by heating.

In the formula, R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by —(OSiR⁷R⁸)_(n)—OSiR⁹R¹⁰R¹¹; R⁷, R⁸, R⁹, R¹⁰, and R¹¹ have the same meanings as R¹ to R⁶; “n” is an integer in the range of 0 to 100; and “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms.

An example of such a method for forming a stretchable film includes a method of mixing a silicon-containing compound shown by the formula (1), a protected or unprotected isocyanate compound, together with a compound that contains a plurality of hydroxy groups for extending the chain length or crosslinking, a compound having an amino group, a catalyst, etc. in certain cases; applying this mixture onto a substrate for peeling to form a film; and heat curing to form a cured film.

As the silicon-containing compound used for this method for forming a stretchable film, the inventive silicon-containing compound described above can be used. As the compound having isocyanate groups, it is possible to use the same isocyanate compound as each of those described in the explanation of the urethane resin.

As the silicon-containing compound shown by the formula (1), it is preferable to use the one shown by the following formula (2).

In this method, a polymer network is formed by increasing the molecular weight while forming urethane bonds through reaction of isocyanate and alcohol. In case of adding a compound that has three or more of hydroxy groups or isocyanate groups, crosslinking reaction proceeds to lower the stretchability, but improve the film strength. Accordingly, it is possible to control the hardness, the stretchability, and the strength by controlling the amount of the compound having two or three hydroxy groups or isocyanate groups. Additionally, an independent stretchable film can be obtained by peeling the film from the substrate for peeling after being cured.

Regarding the molar ratio of the hydroxy groups and isocyanate groups in the composition for forming a stretchable film, it is preferable that the hydroxy groups and isocyanate groups be in the same molar amount, or the molar number of hydroxy groups be larger, that is, the value of the molar number of hydroxy groups divided by the molar number of isocyanate groups be 1 or more. When the molar number of isocyanate groups is smaller, carbon dioxide cannot be formed through the reaction of excess isocyanate groups with water, thereby allowing the film to prevent causing of voids due to foaming. In general, foamed urethane is produced with excess isocyanate groups. In the inventive method for forming a stretchable film, however, the stretchable film is required to have improved strength, and the film is preferably free from void due to foaming thereby.

When the resin in the inventive stretchable film is formed in condition that the molar number of hydroxy groups is larger than that of isocyanate groups as described above, the terminal of the polymer sometimes has a moiety in which a urethane bond is formed at one side of the silicon-containing compound shown by the formula (1) without forming a structure in which urethane bonds are formed at the both sides as in the structure shown by the formula (3). In this case, the terminal of the polymer has a structure shown by the following general formula (3′).

In the formula, R¹ to R⁶ and “A” have the same meanings as defined above.

In the inventive method for forming a stretchable film, the heating temperature is generally set to in the range of room temperature to 200° C. for curing the composition formed to a film. Preferably, the temperature is set to in the range of 40 to 160° C. for the time of 5 seconds to 60 minutes. The heat curing is performed either by coating one side of the composition formed to a film with a peeling film or by coating the both sides of the composition formed to a film. It is preferable to coat one side in curing while being wound on a roll, and the both sides in batch curing, but the method is not limited thereto.

The present invention also provides a method for forming a stretchable film, comprising:

forming a film of a compound having a (meth)acrylate group at a terminal thereof shown by the following formula (4); and

curing the film by heating and/or light irradiation.

In the formula, R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by —(OSiR⁷R⁸)_(n)—OSiR⁹R¹⁰R¹¹; R⁷, R⁸, R⁹, R¹⁰, and R¹¹ have the same meanings as R¹ to R⁶; “n” is an integer in the range of 0 to 100; “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms; R¹² represents a hydrogen atom or a methyl group; “p” and “q” each represent a number of unit in one molecule, and are integers in the range of 1≤p≤100 and 1≤q≤3.

An example of such a method for forming a stretchable film includes a method in which urethane polymer is synthesized by reaction of isocyanate and alcohol, a (meth)acrylate group is formed at the terminal of this urethane polymer shown by the formula (4), and this polymer is formed to a film and cured by heating and/or light irradiation to form a stretchable film. Concretely, this is a method of mixing a silicon-containing compound shown by the formula (1), a protected or unprotected isocyanate compound, and a compound that contains a plurality of hydroxy groups for extending the chain length or crosslinking; followed by polymerization to form a stretchable film using urethane polymer having a polymer terminal of (meth)acrylate. In this case, (meth)acrylate is crosslinked by reaction of radical. As a method for radical crosslinking, addition of a radical generator is desirable. The radical generator includes a thermal-radical generator, which generates a radical by thermal decomposition, and a photo-radical generator, which generates a radical by light irradiation.

The thermal-radical generator is not particularly limited, and illustrative examples thereof include an azo radical generator and a peroxide radical generator. Illustrative examples of the azo radical generator include 2,2′-azobis(isobutyronitrile) (AIBN), 2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2′-azobis(2-methylpropionate), 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis(cyclohexane-1-carbonitrile), and 4,4′-azobis(4-cyanovaleric acid). Illustrative examples of the peroxide radical generator include benzoyl peroxide, decanoyl peroxide, lauroyl peroxide, succinic acid peroxide, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxy pivalate, and 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate.

The photo-radical generator is not particularly limited, and illustrative examples thereof include acetophenone, 4,4′-dimethoxybenzyl, benzyl, benzoin, benzophenone, 2-benzoylbenzoic acid, 4,4′-bis(dimethylamino)benzophenone, 4,4′-bis(diethylamino)benzophenone, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, benzoin isobutyl ether, 4-benzoylbenzoic acid, 2,2′-bis(2-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole, methyl 2-benzoylbenzoic acid, 2-(1,3-benzodioxole-5-yl)-4,6-bis(trichloromethyl)-1,3,5-triazine, 2-benzyl-2-(dimethylamino)-4′-morpholinobutylophenone, 4,4′-dichlorobenzophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,4-diethylthioxanthen-9-one, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 1,4-dibenzoylbenzene, 2-ethylanthraquinone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methylpropiophenone, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone, 2-isonitrosopropiophenone, 2-phenyl-2-(p-toluenesulfonyloxy)acetophenone (BAPO), and camphorquinone.

The loading amount of the thermal-radical generator or the photo-radical generator is preferably in the range of 0.1 to 50 parts by mass based on 100 parts by mass of the resin.

It is also possible to add a crosslinking agent that has a plurality of (meth)acrylate or thiol. This makes it possible to improve the efficiency of radical crosslinking.

It is also possible to add a monomer that has an alkyl group or an aryl group, or a monomer that has a silicon-containing group or a fluorine-substituted alkyl group or aryl group. This makes it possible to decrease the viscosity of the solution to form a stretchable film with thinner thickness. When these monomers each have a polymerizable double bond, they can be fixed into the film in curing the film.

The monomer that has an alkyl group or an aryl group is not particularly limited, and illustrative examples thereof include isobornyl acrylate, lauryl acrylate, tetradecyl acrylate, stearyl acrylate, isostearyl acrylate, behenyl acrylate, adamantane acrylate, phenoxyethyleneglycol acrylate, and phenoxydiethyleneglycol acrylate.

When a stretchable film is formed using a compound that has a (meth)acrylate group at the terminal, the curing can be performed by combining heat-curing and photo-curing. For example, it is possible to form a stretchable film as a base by heat-curing previously, and to form a stretchable film thereon by photo-curing. The photo-curing has merits of inessentiality of heating and capability of short period curing. The area where light does not reach may be cured by heat-curing. When heat-curing and photo-curing are combined, it is possible to select a method for curing in which each merit is applied.

The stretchable film is formed by the method of applying a composition onto a planer substrate or a roll. The method for applying the composition is not particularly limited, and illustrative examples thereof include spin coating, bar coating, roll coating, flow coating, dip coating, spray coating, and doctor coating. The coating is preferably performed so as to have a coating film thickness of 1 μm to 2 mm.

For encapsulating a part with unevenness, it is preferable to use a method such as roll coating and spray coating, or a method for coating a part that requires to be coated by screen printing, etc. In order to perform various coating or printing, the viscosity of the mixed solution have to be controlled. When lower viscosity is required, organic solvent may be added; when higher viscosity is required, filler such as silica is mixed.

The organic solvent is preferably an organic solvent with the boiling point being in the range of 115 to 200° C. at atmospheric pressure. It is preferable to use one or more organic solvents selected from 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, butenyl acetate, isoamyl acetate, phenyl acetate, propyl formate, butyl formate, isobutyl formate, amyl formate, isoamyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate.

In case of curing of the compound that has a (meth)acrylate group at the terminal shown by the formula (4) by heating, the heat curing can be performed with a hot plate, in an oven, or by irradiation of far infrared ray, for example. The heating condition is preferably at 30 to 150° C. for 10 seconds to 60 minutes, more preferably 50 to 120° C. for 30 seconds to 20 minutes. The baking may be performed in any environment such as in the atmosphere, in an inert gas, or in vacuum.

In case of curing of the compound that has a (meth)acrylate group at the terminal shown by the formula (4) by light irradiation, the light irradiation is preferably performed with a light having a wavelength of 200 to 500 nm. As the light source, which is not particularly limited, a halogen lamp, a xenon lamp, excimer laser, and LED can be used, for example. Irradiation with electron beam is also preferable. The irradiation quantity is preferably in the range of 1 mJ/cm² to 100 J/cm².

An example of using the inventive stretchable film is shown in FIGS. 1 and 2. FIG. 1 is a sectional view showing an electrocardiograph in a state being coated with the inventive stretchable film, and FIG. 2 is a schematic drawing of the electrocardiograph in FIG. 1 viewed from the bio-electrode. FIG. 3 is a sectional view showing an electrocardiograph 1 in a state before being coated with the inventive stretchable film, FIG. 4 is a schematic drawing of the electrocardiograph 1 in FIG. 3 viewed from the bio-electrode, and the electrocardiograph 1 in FIGS. 3 and 4 is the one described in Patent Literature 1. As shown in FIGS. 3 and 4, the electrocardiograph 1 is linked to wiring 3 through which three bio-electrodes 2 conduct electric signals and is connected to a center device 4.

As the material of the wiring 3, electrically conductive material are generally used, including metal such as gold, silver, platinum, titanium, and stainless as well as carbon. The wiring can be a bellows form as described in Patent Literature 1 to provide stretchability, and can be formed by pasting powder of the electrically conductive material or wire of the electrically conductive material on a stretchable film, printing electrically conductive ink that contains the electrically conductive material on a stretchable film, or using an electrically conductive fabric in which electrically conductive material and fibers are combined.

The electrocardiograph 1 have to be adhered to skin. Accordingly, in the electrocardiograph 1 in FIGS. 1 to 4, a self-adhesive part 5 is disposed around the bio-electrode 2 in order not to separate the bio-electrode 2 from skin. Incidentally, when the bio-electrode 2 has self-adhesiveness, the surrounding self-adhesive part 5 is inessential.

This electrocardiograph 1 is coated with a stretchable film 6, which is the inventive stretchable film, as shown in FIG. 1. However, the bio-electrode 2 and the self-adhesive part 5 are not coated with the stretchable film 6 as shown in FIG. 2 since they have to be adhered to skin.

When the electrocardiograph 1 is coated with the stretchable film 6, it is possible to coat the back and front sides of the electrocardiograph 1 simultaneously, or coat each side one by one. When the bio-electrode 2 and the self-adhesive part 5, which will be in contact with skin, are left uncoated, the electrocardiograph 1 coated with the stretchable film 6 as shown in FIG. 1 can be obtained such that the electrocardiograph 1 is placed on a substrate 7 with releasability so as to be in contact with the self-adhesive part 5 and is coated with a stretchable film material as shown in FIG. 5, for example, and this is cured by light or heat to form the stretchable film 6, followed by being delaminated from the substrate 7.

Alternatively, illustrative examples thereof include a method in which the bio-electrode 2, the adhesive part 5, and the wiring 3 are formed on the stretchable film 6 to connect the center device 4 as shown in FIG. 6, and then stretchable film material is applied thereon and is cured as shown in FIG. 7 to form a stretchable film 6′. In this case, the bio-electrode 2, the adhesive part 5, and the wiring 3 may be formed on the stretchable film 6 that has been formed on the releasable substrate 7.

Additionally, it is also possible to form the stretchable film 6 on a fabric 8, followed by forming the bio-electrode 2 and the wiring 3 thereon to connect the center device 4 as shown in FIG. 8, and to form the stretchable film 6′ thereon to coat the wiring 3 and the center device 4 as shown in FIG. 9. In this case, the cloth equipped with the device is possibly washed. Accordingly, the stretchable film is possibly required to have higher mechanical strength, water resistance, stretchability, adhesion to a cloth, adhesion to a device, and sealing properties of a device that are durable to washing.

Incidentally, when the stretchable film 6 or 6′ is formed on parts having unevenness as shown in FIGS. 5, 7, and 9, the above described methods are preferable such as roll coating, spray coating, and a method to coat a part that is required to be coated by screen printing, etc.

Alternatively, when the stretchable film 6′ is formed on the stretchable film 6 as shown in FIGS. 7 and 9, the use of a compound shown by the formula (3) makes it possible to form the stretchable film 6 previously by heat curing, and to form the stretchable film 6′ thereon by photo-curing.

The inventive method for forming a stretchable film described above makes it possible to easily form a stretchable film that has excellent stretchability and strength equal to or superior to those of polyurethane, with the film surface having high repellency.

EXAMPLES

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Incidentally, the weight average molecular weight (Mw) represents a weight average molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC).

Synthesis Example 1 Synthesis of Silicon-Containing Compound-1

The reaction shown by the following formula (5) was performed. Into a 200 mL four-neck flask, 22.5 g of Material (1-II) in which two hydroxy groups of pentaerythritol had been protected by α,α-dichlorotoluene and 0.06 g of PL-50N (platinum catalyst solution, manufactured by Shin-Etsu Chemical Co., Ltd.) were introduced, and the temperature was increased to 55° C. using an oil bath in a nitrogen atmosphere. Then, 44.5 g of heptamethyltrisiloxane was added dropwise over 2.5 hours using a 100 mL dropping funnel. This was stirred for 3 hours after finishing the dropping addition, and then the temperature was returned to room temperature by removing the oil bath. This was subjected to deprotection reaction by adding 50 g of methanol, 1 g of methanesulfonic acid, and 10 g of water, followed by stirring at 50° C. for 1 hour. The solution was neutralized by adding 10 g of sodium bicarbonate, followed by vacuum distillation to give 49.3 g of Silicon-containing compound-1 (1-IV) (yield: 74%) having the following characteristics.

Silicon-Containing Compound-1 (1-IV)

Colorless Liquid

¹H-NMR (500 MHz, Acetone-d6): δ=0.02 (6H, m), 0.11 (36H, m), 0.46 (4H, m), 1.30 (8H, s), 3.45 (2H, dd), 3.46 (2H, s), 3.57 (2H, dd)

Synthesis Examples 2 to 6 Synthesis of Silicon-Containing Compounds-2 to 5, Comparative Silicone-pendant diol Compound-1

Silicon-containing compounds-2 to 5 and Comparative silicone-pendant diol compound-1 were synthesized by the same reaction as in Synthesis Example 1 except for using other materials.

The following are Silicon-containing compounds-1 to 5, Comparative silicone-pendant diol compound-1 (comparative silicon-containing compound-1), Isocyanate compounds-1 to 5, and Hydroxy compounds-1 to 8 blended to compositions for forming a stretchable film.

(In the formulae, the number of repeating units each represent the average value.)

(In the formulae, the number of repeating units each represent the average value.)

Synthesis Example 7 Synthesis of Silicone-pendant urethane-(meth)acrylates-1 to 8, Comparative urethane-(meth)acrylate-1

Each Silicone-pendant urethane-(meth)acrylate blended as a compound having a (meth)acrylate group at the terminal thereof was synthesized as follows.

A mixture of 1 mole of Hydroxy compound-5, 1 mole of Hydroxy compound-8, and 1 mole of Silicon compound-1 was heated at 60° C. and subjected to vacuum drying to remove water. To this, 4 mole of isophorone diisocyanate was added, and 0.01 mole of dibutyl tin dilaurate was added to react at 60° C. for 3 hours while stirring. To this, 2 mole of hydroxyethyl acrylate was added to react at 60° C. for 3 hours while stirring, and Silicone-pendant urethane-(meth)acrylate-1 was obtained thereby. The obtained polymer was measured for ¹³C-NMR, ¹H-NMR, and GPC to give following analytical results.

In a similar manner, each of Silicone-pendant urethane-(meth)acrylates-2 to 8 and Comparative urethane-(meth)acrylate-1 was synthesized by mixing a hydroxy compound(s), a silicon compound, an isocyanate compound, and a tin compound of a catalyst to react.

The following are Silicone-pendant urethane-(meth)acrylates-1 to 8 and Comparative urethane-(meth)acrylate-1 blended to compositions for forming a stretchable film as a compound having a (meth)acrylate group at the terminal.

(In the formulae, the numbers of repeating unit each represent the average value, t¹+t² is 20 on average, and t³ is 10 on average.)

The following are Photo-radical generators-1 to 3 and Thermal-radical generator-1 blended to compositions for forming a stretchable film as an additive.

-   Photo-radical generator-1: 4,4′-dimethoxybenzyl -   Photo-radical generator-2: 2,2-dimethoxy-2-phenylacetophenone -   Photo-radical generator-3: (±)-camphorquinone -   Thermal-radical generator-1: dimethyl     2,2′-azobis(2-methylpropionate)

The following is an organic solvent blended to compositions for forming a stretchable film.

Organic solvent: propylene glycol monomethyl ether acetate (PGMEA)

Examples 1-1 to 1-6, Comparative Example 1-1

The silicon-containing compound, the isocyanate compound, the hydroxy compounds, and a catalyst were mixed in each composition described in Table 1. This was defoamed to prepare a composition for forming a stretchable film (Stretchable film materials 1-1 to 1-6, Comparative stretchable film material 1-1). After the defoaming, each of Stretchable film materials 1-1 to 1-6 and Comparative stretchable film material 1-1 was applied onto a polyethylene substrate by bar coating method, followed by baking at 130° C. for 20 minutes under nitrogen atmosphere to produce a stretchable film (Films 1-1 to 1-6, Comparative Film 1-1) on the substrate. The ratio of molar numbers of hydroxy groups and isocyanate groups in each composition for forming a stretchable film is shown in Table 1.

TABLE 1 Silicon- pendant diol Isocyanate compound compound Catalyst Molar Stretchable film (parts by (parts by Hydroxy compounds (parts by ratio material mass) mass) (parts by mass) mass) hydroxy/isocyanate Stretchable film Silicon- Isocyanate Hydroxy compound-8 (5) Dibutyl tin 1.05 material 1-1 containing compound-1 Hydroxy compound-2 (1) dilaurate compound-1 (3) (11) Hydroxy compound-4 (10) (0.01) Stretchable film Silicon- Isocyanate Hydroxy compound-5 (15) Dibutyl tin 1.06 material 1-2 containing compound-2 Hydroxy compound-8 (9) dilaurate compound-2 (3) (6) Hydroxy compound-3 (0.5) (0.01) Stretchable film Silicon- Isocyanate Hydroxy compound-6 (28) Dibutyl tin 1.04 material 1-3 containing compound-3 Hydroxy compound-3 (0.5) dilaurate compound-3 (5) (4) (0.01) Stretchable film Silicon- Isocyanate Hydroxy compound-6 (28) Dibutyl tin 1.03 material 1-4 containing compound-3 Hydroxy compound-7 (3) dilaurate compound-4 (5) (6.5) Hydroxy compound-3 (0.5) (0.01) Stretchable film Silicon- Isocyanate Hydroxy compound-6 (20) Dibutyl tin 1.07 material 1-5 containing compound-4 Hydroxy compound-7 (2.5) dilaurate compound-1 (5) (12) (0.01) Stretchable film Silicon- Isocyanate Hydroxy compound-6 (20) Dibutyl tin 1.04 material 1-6 containing compound-5 Hydroxy compound-7 (4) dilaurate compound-5 (5) (12) (0.01) Comparative Comparative Isocyanate Hydroxy compound-1 (5) Dibutyl tin 1.03 stretchable film silicone- compound-1 Hydroxy compound-8 (3) dilaurate material 1-1 pendant diol (11) Hydroxy compound-4 (8) (0.01) compound-1 (5) Hydroxy compound-2 (1)

Examples 2-1 to 2-7, Comparative Example 2-1

Each of the compound having a (meth)acrylate group at the terminal, Photo-radical generators-1 to 3, and Thermal-radical generator-1 was mixed in the composition described in Table 2 to prepare a composition for forming a stretchable film (Stretchable film materials 2-1 to 2-7, Comparative stretchable film material 2-1). Each prepared composition for forming a stretchable film was applied onto a polyethylene substrate by bar coating method. In cases of Stretchable film materials 2-1 to 2-5 and 2-7, and Comparative stretchable film material 2-1, the coated film of each composition was cured by irradiation of 500 mJ/cm² of light with a 1,000 W xenon lamp in a nitrogen atmosphere to produce a stretchable film (Films 2-1 to 2-5, 2-7, Comparative Film 2-1). In case of Stretchable film material 2-6, the prepared compositions for forming a stretchable film was applied onto a polyethylene substrate by bar coating method, followed by baking at 120° C. for 20 minutes in a nitrogen atmosphere to produce a stretchable film (Film 2-6).

TABLE 2 Stretchable film Compound having (meth) acrylate group Additive material (parts by mass) (parts by mass) Stretchable film Silicone-pendant urethane-(meth)acrylate-1 (70) Photo-radical material 2-1 Isobornyl acrylate (30) generator-1 (3) Stretchable film Silicone-pendant urethane-(meth)acrylate-2 (85) Photo-radical material 2-2 Silicone-pendant urethane-(meth)acrylate-4 (15) generator-2 (3) Stretchable film Silicone-pendant urethane-(meth)acrylate-3 (75) Photo-radical material 2-3 Silicone-pendant urethane-(meth)acrylate-5 (25) generator-3 (3) Stretchable film Silicone-pendant urethane-(meth)acrylate-1 (60) Photo-radical material 2-4 Silicone-pendant urethane-(meth)acrylate-6 (40) generator-3 (3) Stretchable film Silicone-pendant urethane-(meth)acrylate-2 (70) Photo-radical material 2-5 Silicone-pendant urethane-(meth)acrylate-7 (30) generator-3 (3) Isobornyl acrylate (30) Stretchable film Silicone-pendant urethane-(meth)acrylate-2 (70) Thermal-radical material 2-6 Silicone-pendant urethane-(meth)acrylate-7 (30) generator-1 (3) Isobornyl acrylate (30) Stretchable film Silicone-pendant urethane-(meth)acrylate-8 (70) Photo-radical material 2-7 Isobornyl acrylate (30) generator-1 (3) Comparative Comparative urethane-(meth)acrylate-1 (70) Photo-radical stretchable film Isobornyl acrylate (30) generator-1 (3) material 2-1 (Measurement of Film Thickness, Contact Angle, Stretching Property, and Strength)

The film thickness was measured on each stretchable film after curing, together with contact angle with water on the surface thereof. After measuring the contact angle with water on the surface of the stretchable film, the stretchable film was peeled from the substrate, and subjected to measurement of the stretching property and strength in conformity to JIS K 6251. The results are shown in Table 3.

TABLE 3 Stretchable Stretchable film Film thickness Contact Elongation Strength film material (μm) angle (°) (%) (MPa) Example 1-1 Film 1-1 Stretchable film 310 116 320 15.1 material 1-1 Example 1-2 Film 1-2 Stretchable film 320 115 400 12.1 material 1-2 Example 1-3 Film 1-3 Stretchable film 310 116 440 10.6 material 1-3 Example 1-4 Film 1-4 Stretchable film 350 118 350 11.6 material 1-4 Example 1-5 Film 1-5 Stretchable film 360 118 410 12.6 material 1-5 Example 1-6 Film 1-6 Stretchable film 330 113 390 13.6 material 1-6 Example 2-1 Film 2-1 Stretchable film 270 115 310 13.0 material 2-1 Example 2-2 Film 2-2 Stretchable film 260 115 290 11.4 material 2-2 Example 2-3 Film 2-3 Stretchable film 370 115 250 12.1 material 2-3 Example 2-4 Film 2-4 Stretchable film 370 112 290 11.8 material 2-4 Example 2-5 Film 2-5 Stretchable film 370 115 220 12.7 material 2-5 Example 2-6 Film 2-6 Stretchable film 310 113 220 16.2 material 2-6 Example 2-7 Film 2-7 Stretchable film 310 118 280 13.2 material 2-7 Comparative Comparative Comparative 300 93 350 2.3 Example 1-1 Film 1-1 stretchable film material 1-1 Comparative Comparative Comparative 330 81 290 12.1 Example 2-1 Film 2-1 stretchable film material 2-1

As shown in Table 3, each stretchable film exhibited higher contact angle with water, that is, high repellency, together with excellent stretchability and strength in Examples 1-1 to 1-6, in which a diol compound having two pendant silicon-containing groups reacted with an isocyanate compound, and in Examples 2-1 to 2-7, in which a compound having two pendant silicon-containing groups was used as a compound having a (meth)acrylate group at the terminal.

On the other hand, the stretchable film in Comparative Example 2-1, in which a compound without having a siloxane bond was used as a compound having a (meth)acrylate group at the terminal, exhibited lower contact angle with water, that is, lower water repellency, and inferior strength compared to Examples 1-1 to 1-6 and 2-1 to 2-7. The stretchable film in Comparative Example 1-1, in which the conventional diol compound having a linear pendant silicone reacted with an isocyanate compound, exhibited inferior strength, particularly compared to that of Example 1-1, in which the composition was same except for the silicon-containing groups, although the contact angle with water was high.

From the above, it was revealed that the inventive stretchable film has excellent stretching property and strength, together with excellent water repellency on the film surface, and has excellent properties as a film to coat stretchable wiring used for a wearable device, etc. thereby. The stretchable film containing the urethane resin having such excellent properties of the present invention also has excellent resistance to washing since it has higher mechanical strength, water resistance, stretchability, adhesion to a cloth, adhesion to a device, and sealing properties of a device that are durable to washing even when a cloth equipped with a device having the stretchable film is washed.

It is to be noted that the present invention is not restricted to the foregoing embodiment. The embodiment is just an exemplification, and any examples that have substantially the same feature and demonstrate the same functions and effects as those in the technical concept described in claims of the present invention are included in the technical scope of the present invention. 

The invention claimed is:
 1. A urethane resin comprising a structure containing a (meth)acrylate group at a terminal thereof shown by the following formula (4):

wherein R¹, R², R³, R⁴, R⁵, and R⁶each independently respresent a linear, branched, or cyclic alkyl group having 1 to 6 atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by -(0SiR⁷R⁸)_(n)-OSiR⁹R¹⁰R¹¹; R⁷, R⁸, R⁹, R¹⁰, and R¹¹ have the same meanings as R¹ to R⁶; “n” is an integer in the range of 0 to 100; “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms; R¹² represents a hydrogen atom or a methyl group; and “p” and “q” each represent a number of unit in one molecule, and are integers in the range of 1≤p≤100 and 1≤q≤3.
 2. A stretchable film comprising the urethane resin according to claim
 1. 3. The stretchable film according to claim 2, wherein the stretchable film exhibits a stretching property of 40 to 500% in a tensile test regulated by JIS K
 6251. 4. The stretchable film according to claim 3, wherein the stretchable film is used as a film to be in contact with a conductive wiring having stretchability.
 5. The stretchable film according to claim 2, wherein the stretchable film is used as a film to be in contact with a conductive wiring having stretchability.
 6. A method for forming a stretchable film, comprising: mixing a compound shown by the following formula (1) and a compound having an isocyanate group to make a mixture.

forming a film of the mixture; and curing the film by heating.
 7. A method for forming a stretchable film, comprising: forming a film of a compound having a (meth)acrylate group at a terminal thereof shown by the following formula (4):

wherein R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, a 3,3,3-trifluoropropyl group, or a group shown by —(OSiR⁷R⁸)_(n)—OSiR⁹R¹⁰R¹¹; R⁷, R⁸, R⁹, R¹⁰, and R¹¹ have the same meanings as R¹ to R⁶; “n” is an integer in the range of 0 to 100; “A” represents a linear or branched alkylene group having 1 to 6 carbon atoms; R¹² represents a hydrogen atom or a methyl group; “p” and “q” each represent a number of unit in one molecule, and are integers in the range of 1≤p≤100 and 1≤q≤3; and curing the film by heating and/or light irradiation. 